U.S. Pat. No. 5,317,036 teaches the gas-phase polymerization of olefins with metallocene catalysts in liquid form. In such systems resin particle size can be controlled by spraying the liquid catalyst into a zone which is substantially free of resin as disclosed in U.S. Pat. No. 5,693,727, which is incorporated herein by reference. However, it is difficult to control the use of these catalysts because of their high activity.
Supported metallocene catalysts are also known, but these lack high activity and are expensive on a polymer pound basis. Thus, it is desirable to avoid these problems.